Energetics Flashcards
Definition of enthalpy change:
Enthalpy change (delta H), is the heat energy transferred in a reaction at constant pressure the units are kJ mol^-1
Enthalpy change is the…
Heat energy change measured under constant conditions and constant pressure.
Formula for enthalpy change of reaction?
Total energy absorbed - Total energy released
Definition of standard enthalpy of formation:
Standard enthalpy of formation is the enthalpy change when one mole of a compound is formed from its elements in their standard states under standard conditions.
Definition of standard enthalpy of combustion:
Standard enthalpy of combustion is when one mole of a substance is completely burned in oxygen under standard conditions.
Define Hess’s Law:
The total enthalpy change is independent of the route taken
Definition of a calorimeter:
The apparatus used to measure temperature changes in energy is transferred during a chemical reaction.
Definition of colorimetry:
This is a method used to measure enthalpy changes in chemical reactions.
Definition of reaction rates:
Reaction rate is defined as the change in concentration or amount of reactant or product over time.
Increasing the temperature does want to a reaction?
It decreases the rate of the reaction.
How does increasing the concentration also increase reaction rate?
If you increase the concentration of reactants in the solution the particles are on average closer together. If they’re closer together they’ll collide more often. If they collide more frequently they’ll have more chances to react.
How does increasing pressure increase the rate of reaction?
Increasing the pressure works in the same way as increasing concentration. Raising the pressure pushes the gas particles are closer together making the more likely to collide. So collisions take place more frequently and the reaction rate increases.
Definition of a catalyst:
A catalyst is a substance that increases the rate of a reaction by providing an alternative reaction pathway with a lower activation energy. The catalyst is chemically unchanged at the end of the reaction.
Definition of Le Chatelier’s principle?
If a reaction at equilibrium is subjected to a change in concentration, pressure or temperature, the position of equilibrium will move to counteract the change.
